DE-PS 27 50 868 discloses a so-called auxiliary tool for boring dowel holes in boards which are to be connected to each other by dowels or pegs when in end face planar contact. The auxiliary tool comprises a plate placeable upon the board to be drilled and at least one guide hole for a drilling tool bit has been worked into this plate. A dowel engagement portion is allocated to each guide hole, which comprises a planar board contact face parallel to the central axis of the guide hole and at least one peg engagement slot open towards the board contact face. Herein, the internal width of the dowel or peg engagement slot is configured to be equal to the diameter of the guide hole. Finally, the central axes of the dowel engagement slot and the guide hole lie in a common plane perpendicular to the board contact.
Such an auxiliary tool is handled with the board, which has to be drilled on its end face and is provided with a quantity of holes which must not have an accurately predetermined spacing from one another. Dowels or pegs are temporarily installed in all dowel holes drilled into this board. Subsequently, this board, provided with dowel holes and dowels, is clamped snugly to the other undrilled board in a workbench or the like. The auxiliary tool is placed in such a way upon the boards, that the dowel engagement portion, with its dowel engagement slot, embraces a dowel or peg protruding from the dowel hole. The guide hole or the drilling bit, allocated to the dowel engagement slot, is brought into such a position, that an extremely accurate alignment of the dowel holes in both boards receiving a dowel or peg is assured. After the position of all dowels inserted into a board has been probed in this way and the matching aligned holes have been drilled in the other board, all the dowels or pegs inserted into the dowel holes of the one board are again removed. After that there follows the usual connection of both boards by adhesive or bonding, wherein one dowel or peg projects into the aligned dowel holes of the two boards to be connected with one another.
The known auxiliary tool requires the dowel or peg to always be inserted into the matching dowel hole of the first board which, prior to connecting both boards by adhesion or bonding must again be removed, in order to produce an aligned dowel hole in the second board. This is not only cumbersome, but also time consuming. This additional work is required for each aligned pair of dowel holes, wherein at least two dowels for the corresponding dowel holes must be used in the region of two boards to be connected with each other by doweling or pegging and said adhesion or bonding. Furthermore, if the dowel or peg is not manufactured with great accuracy and inserted into the dowel hole under stress, it can be damaged or even destroyed if it is pulled out of the dowel holes. If clearance or play exists between the dowels or pegs and the dowel bore in the first board, positional accuracy of the dowel holes in the second board is greatly impaired. The previously known auxiliary tool is limited to a maximum of three guide holes because of the upright lugs for alignment of the guide hole to the end face of a board. If guide holes with another diameter are required, another auxiliary tool must be used.
It is therefore an object of the invention to provide a jig for boring of dowel holes in true alignment with one another in two boards or the like to be connected by dowels or pegs and adhesion or bonding.
Another object of the invention is to provide a jig where a required insertion and removal of pegs into the dowel holes of a board for positional determination of the bores in the second board is no longer necessary.